Nonaqueous drilling fluid



Patented Nov. 26, 1940 '5 UNITED sr 'rss NONAQUEOUS panama mum l leginaldDavidDawson, Tiepoaandl'hilippus i I Hende'rikus Huisman, I

ranrkalan Brandan, Dutch East Indies, assignors to Shell Development Company, San ration of Delaware Francisco, Calif, a oorpo- Y L Y Noni-swing. ApplicationMay 31,1939,8erlalNo.

276,632. IntheNetherlandsJuneZ, 1m

momma (o1. 255-1) The present invention relates to improvements in drilling fluids for oil-and gas wells and per-, tains more particularly to the oil-base type. Non-aqueous drilling. fluids or muds are usu- 5 ally prepared in a manner analogous to the preparation oi clay-water base muds, that is, by suspending flnely divided substances, such as haematite, galena, barytes, burnt clay, silica, crushed oyster shells, etc., in oils, e. g. mineral oils or fractions thereof such as gas oils. Various substances such as alkaline soaps, voluminousflmagnesium carbonate or oxide, etc., are added, it necessary, to prevent the settling out 01' the solid particles. It has also been .proposed to add natural or synthetic asphalt. for the purpose of impro ng the deplastering properties of these muds. v

However, an outstanding deterent to the use of these nonaqueous drilling fluids is their unsatisfactory plastering properties, that is, their inability to prevent excessive loss 01' fluid to the formation and loss of production due to clogging of the. pores of the oil-bearing formations by penetration thereinto by the drilling fluids'an'd their. contained solids. A thin, adherent and impermeable .mud sheath must be formed on the walls of the borehole to prevent these undesirs able occurrences.

idative treatment, i. e., have been exposed to the influence of air, oxygen, chlorine, permanganate and the like-at elevated temperatures, to methods, welllmown to those skilled in'the so-that loss of drilling fluid-during drilling through porous strata is eliminated. Conversely, drilling fluids treated with asphaltic bitumens not previously subjected to an oxidative treatment, such as normal steam asphalts, donot show this desirable property. As illustrative of -the advantages of drilling fluids prepared 'according to our invention, .Table I shows drilling fluids containing blown and non-blown asphalts;

compared in a standard fluids were prepared by adding 20 parts by weight of :the asphalt to a suspension of 126 parts of finely divided magnetite in'64 parts of crude oil which had been topped to 200 C. .The initial used in these permeabilities oi the core samples tests were nearly the same. 5

Table 1 Kind oi asphalt mm (1% in muddlng-oi! machine, in which low displacement oi, fluid through the mud sheath is indicative of a drilling fluid hav-' ing desirable plastering properties. The drilling eowreenensols blown" asphalt imparts to drilling fluids the desirable plastering properties, i. e., capable of low liquid displacement, while muds treated with non-blown asphalts' are poor in these properties.

As will be noted, this phenomenon is independent of the source of the asphalt The above-mentioned favorable property is more pronounced as the oxidative treatment of the asphalt bitumens is further continued as may be seen from Table 11 below. For this pur- It is apparent from the above table that pose two kilograms of an asphalt were blown as highly as possible at a temperature of 300 0. Five gram samples were taken at each period indicated in the table, and incorporated in a suspension of 126 grams of finely ground magnetite in 62.5 grams oi a crude oil which had been topped to 200 C. and tested in the mudding-ofl. machine as above.

We claim as our invention:

1. A nonaqueous drilling fluid comprising oil, finely divided solid material and blown asphaltic bitumen.

2. A nonaqueous drilling fluid comprising oil, 5 finely ground magnetite, and blown asphaltic bitumen.

3. A nonaqueous drilling fluid comprising oil,

Table II 10 MLoidisplaocment Softening Penetra- Asphutem Viscosity 0! literigf' Treatment oiasphalt fig 6 content, 539

' c. mm MaoMichael 1 40 no I min. min. min. 1

s4 45 19.4 a ass as as 24.0 a 21.2 no 10.5 ass a 10.0

m an 39.0 a as 10.5 1 s 141 a 4&1 4 0.0 4.7 1.2 140 4.5 43.6 4 0.0 4.5 an

As will be seen from Table II, the improvement in plastering properties of muds increases as the degree of oxidation of the asphalt increases.

5 The effect of blown asphalt on the plastering properties of muds might be explained by assuming the formation, during the oxidative treatment of the asphalt bitumens of very fine solid particles which do not occur in natural or artificial 30 asphalt bitumens and the fineness of which cannot even be approximated by very intensive grinding of solid substances, such as porcelanite or zinc oxide.

In general, a drilling fluid prepared according 5 to the present invention contains about 5 to 15% of blown asphaltic bitumens and 30 to 60% of a finely divided solid or weighting material suspended in an 011, although greater or lesser amounts may be used, if desired.

Various weighting and settling inhibitors may be added to drilling fluids containing blown asphalts. For example, a composition which may be used for drilling wells comprises 9.8 parts by weight blown asphalt, having a softening point 45 (R 8: B) of 107 C. and penetration at C. of 15 mm., 49.5 parts of stove oil, and 40.7 parts of ground oyster shells. Another composition which was found to be effective in completing an oil well consisted of 51.9% absorption oil, 84.7%

50 ground shell, 9.9% blown asphalt, having the same properties as the aforementioned asphalt, and 3.5% of a settling inhibitor, such as lampblack or carbon black.

finely ground oyster shells, and blown asphaltic bitumen.

4. A nonaqueous drilling fluid comprising oil, finely ground oyster shells, a settling inhibitor, 25

and blown asphaltic bitumen.

5. A nonaqueous drilling fluid comprising 5 to 15%. of blown asphaltic bitumensand to 60% of a finely divided solid material suspended in an oil. 30

6. A nonaqueous drilling fluid comprising oil, finely divided solid material, blown asphaltic bitumen, and lamp black as a settling inhibitor.

7. In drilling oil and gas wells, the step of circulating in the borehole during drilling an oilbase drilling fluid comprising a blown asphaltic bitumen.

8. In drilling oil and gas wells, the step of circulating in the borehole during drilling an oilbase drilling fluid comprising a blown asphaltic g bitumen and lamp black. k

9. A nonaqueous drilling fluid comprising 011,.

a finely divided solid material, a settling inhibitor, and blown asphaltic bitumen.

10. In drilling oil and gas wells, the step of circulating in the borehole an oil base drilling fluid comprising a finely divided solid material, a settling inhibitor, and blown asphaltic bitumen.

REGINALD pavm DAWSON. so mmmus rmmamrxus HUISMAN. 

